In plane switching liquid crystal displaying apparatus for improving luminance

ABSTRACT

An IPS liquid crystal displaying apparatus includes: a TFT array substrate, an opposite substrate opposed to the TFT array substrate and liquid crystal interposed between the TFT array substrate and the opposite substrate, wherein the TFT array substrate is composed of a glass substrate, a gate insulating film formed on the glass substrate, a possivation film formed on the gate insulating film, a plurality of scanning lines for transmitting a scanning signal, a plurality of signal lines for transmitting an image signal, a plurality of pixels arranged in grid like pattern by crossing the plurality of scanning lines with the plurality of signal lines, a plurality of TFTs implementing switching operation of the image signal on the basis of the scanning signals, a plurality of driving electrodes connected with the TFT, a plurality of opposite electrodes arranged in such a manner that each of the plurality of opposite electrodes is opposed to each of the driving electrodes, and a plurality of common lines for mutually connecting each of the opposite electrode of one of the plurality of pixels with the other one of the plurality of pixels, wherein the TFT array substrate is formed on the passivation film, the passivation film being different from a layer provided with the driving electrode and the opposite electrode.

BACKGROUND OF THE INVENTION

The present invention relates to an IPS (In Plane Switching) liquidcrystal displaying apparatus by generating an electric field parallel toan array substrate to drive the liquid crystal. More particularly, thepresent invention relates to a construction of a highly bright liquidcrystal displaying apparatus increased in aperture ratio by reducinginfluences of the leakage of electric field from a signal line, therebyreducing the light shielding area.

In an active matrix type liquid crystal displaying apparatus, an IPSsystem where the direction of the electric field to be applied on theliquid crystal is made parallel to the array substrate is mainly used asa method of obtaining a wider viewing angle (for example, see JapaneseUnexamined Patent Publication No. 254712/1996). It is reported that thissystem enables to remove the almost all of the change in the contrastand the inversion of the gradation level in changing the viewing-angledirection (see, for example, AsiaDisplay, 95, page, 577 to 580 by M.Oh-e, and others).

A construction of one pixel of the conventional IPS liquid crystaldisplaying apparatus is depicted in FIGS. 43a and 43 b. FIG. 43a is theplain view thereof. FIG. 43b is a sectional view taken along a line A—Aof FIG. 43a. FIG. 44 is a circuit diagram showing an equivalent circuitof one pixel of the pixel electrode of an IPS liquid crystal displayingapparatus. FIG. 45 is a circuit diagram for illustrating the circuit ofthe IPS liquid crystal displaying apparatus. Referring to FIGS. 43a and43 b, reference numeral 1 denotes a glass substrate, numeral 2 denotes ascanning line, numeral 3 denotes a signal line, numeral 4 denotes a thinfilm transistor (TFT), numeral 5 denotes a driving electrode, numeral 6denotes an opposite electrode, numeral 7 denotes an electrode forforming the storage capacitance, numeral 8 denotes common line, numeral9 denotes a gate insulating film, numeral 10′ denotes a passivationfilm, numeral 11 denotes a liquid crystal, numeral 12 denotes a BM(black matrix), numeral 14 denotes a contact hole, numeral 15 denotes asource electrode, and numeral 16 denotes a drain electrode. Numeral 20denotes an array substrate comprising glass substrate 1, a signal line3, a driving electrode 5, an opposite electrode 6. Numeral 30 denotes anopposite substrate arranged opposite to the array substrate 20. Numeral40 denotes a slit which is a gap between the signal line 3 and theopposite electrode 6, and numeral 50 denotes an opening. Referring toFIG. 44 and FIG. 45, the same reference numerals as those of FIGS. 43aand 43 b depict the same parts or its equivalents as those of FIGS. 43aand 43 b.

The construction and operation of the conventional IPS liquid crystaldisplaying apparatus will be described according to FIGS. 43a and 43 b,FIG. 44 and FIG. 45. Referring to FIG. 45, a plurality of grid shapedpixels encircled by the scanning line 2 and the signal line 3 can bemade by crossing, at an approximately right angle between a scanningline 2 connecting the scanning line driving circuit 102 and a signalline 3 connecting the signal line driving circuit 101. A TFT (Thin FilmTransistor) is provided at each intersection point between a signal lineand a scanning line for forming the grid shaped pixel. Numeral 103denotes a circuit for common lines.

This condition is shown by an equivalent circuit in FIG. 44. The TFT 4is a semiconductor element having three electrodes of a gate electrode,a source electrode 15 and a drain electrode 16. The gate electrode isconnected with a scanning line 2 extended from the scanning line drivingcircuit. The source electrode 15 is connected with a signal line 3connected with the signal line driving circuit. The remaining drainelectrode 16, connected with the driving electrode 5, drives the liquidcrystal by an electric field caused between the driving electrode 5 andthe opposite electrode 6. Numeral 7 denotes a storage capacitance forstoring the electric charge between the driving electrode 5 and theopposite electrode 6. The construction of one pixel will be described inaccordance with FIG. 43a and FIG. 43b. In a pixel formed through thecrossing between the scanning line 2 and the signal line 3 are provideda driving electrode 5 for driving the liquid crystal layer, an oppositeelectrode 6 and a TFT 4. In the TFT 4 there are three electrodes. Thescanning line 2 connected with the scanning line driving circuit shownin FIG. 45 is connected with the gate electrode of the TFT 4, so as toapply the scanning signal, the scanning line driving circuit outputs,upon the gate electrode of the TFT 4.

The signal line 3 connected with the signal line driving circuit isconnected with the source electrode 15 of the TFT 4 to transmit theimage signal the signal line driving circuit outputs. The drainelectrode 16 of the TFT 4 is connected with the driving electrode 5through a contact hole 14 as shown in FIG. 43a. In the same pixel, anopposite electrode 6 is provided to be engaged face to face with thedriving electrode 5. The opposite electrode 6 is connected with thecommon line 8. The common line 8 is connected with each oppositeelectrode 6 provided in each pixel on the TFT array substrate 20.

The sectional construction of the picture section will be described inaccordance with FIG. 43b. A driving electrode 5 and an oppositeelectrode 6 are respectively formed on the glass substrate 1. Althoughnot shown in FIG. 43b, the scanning line 2 and the common line 8 arealso formed in the same layer as that of the driving electrode 5 and theopposite electrode 6. The gate insulating film 9 is laminated on a glasssubstrate by covering the driving electrode, the opposite electrode, thescanning line and the common line, and the signal line 3 is formed onthe gate insulating film 9. Although not shown in FIG. 43b, the storagecapacitance forming electrode 7 is also formed in the same layer as thatof the signal line 3. A passivation film 10′ is laminated further on thesignal line 3, so as to form the TFT array substrate 20. The TFT arraysubstrate 20 and the opposite substrate 30 is superposed. The IPS liquidcrystal displaying apparatus is made with a liquid crystal 11 beingsealed between the TFT array substrate 20 and the opposite substrate 30.

The IPS liquid crystal displaying apparatus is a system where theelectric filed is caused along the surface of the TFT array substrate 20between the driving electrode 5 and the opposite electrode 6 provided onthe TFT array substrate 20. Thus, the opposite substrate 30 is ano-electrode substrate having no electrode. On the opposite substrate 30there is provided a BM 12 which is a light shielding film. Although notshown, the light leaked from a slit 40 of FIG. 43a is to be shieldedwith a back light, provided on the under side of the TFT arraysubstrate, as a light source in FIG. 43b.

An area surrounded by broken lines shown by 50, defining an opening perpixel, functions as a role of a window through which light passes withthe back light as a light source. But the light from the back light isshielded by a driving electrode 5, an opposite electrode 6, a blackmatrix 12 and so on, thereby influencing upon the picture quality of theliquid crystal display. Thus, a problem is to reduce the ratio, in area,of the driving electrode 5, the opposite electrode 6, the black matrix12 and so on to be occupied in the area of the opening 50.

The above description is given about the construction of the pixel ofthe conventional IPS liquid crystal displaying apparatus about FIGS. 43aand 43 b, FIG. 44 and FIG. 45. The operation of the IPS liquid crystaldisplaying apparatus will be described. The gate electrode is providedin each pixel. The gate electrode of the TFT is connected with thescanning line 2. The source electrode 15 is connected with the signalline 3. The drain electrode 16 is connected with the driving electrode5. Such a TFT 4 is a semiconductor switching element, which controls thedriving operation of the liquid crystal of each pixel. When a scanningsignal is applied, through the scanning line 2 from the scanning linedriving circuit, upon the gate electrode of the TFT 4, all the TFT 4 ofthis horizontal line is respectively switched on.

When the gate electrode is switched on, the image signal transmittedfrom the signal line driving circuit flows to the drain electrode 16 byway of the source electrode 15 and is stored in the driving electrode 5connected with the drain electrode 16. Electric charge applied in thedriving electrode 5 is stored with respect to the opposite electrode 6and the gate electrode is turned on again. The electric charge of thattime is stored before the new image signal electric charge is applied.The driving electrode 5 and the opposite electrode 6 function as acapacitor in that the electric charge is stored while the gate electrodeis on, and the stored electric charge is held as it is when the gateelectrode is turned off. The storage capacitance 13 shown in FIG. 44increases the accumulating force of the capacitance. The storagecapacitance 13 is formed by the vertical lamination of the storagecapacitance electrode 7 and the common line 8 through the gateinsulating film 9.

In the conventional IPS liquid crystal displaying apparatus shown inFIGS. 43a and 43 b, between the signal line 3 provided in the side endportion of one pixel and the opposite electrode 6 formed in parallel tothe signal line 3 is caused an electric field due to the potentialdifference between the signal line 3 and the opposite electrode 6. FIG.46 is a view showing influences to be applied, upon the electric fieldto be caused between the driving electrode 5 and the opposite electrode6, by the electric field caused between the signal line 3 and theopposite electrode 6 of the conventional IPS liquid crystal displayingapparatus, which has the TFT array substrate where the driving electrode5 and the opposite electrode 6 are formed in the layer lower than thesignal line 3. In FIG. 46, changes in the potential caused between thedriving electrode 5 and the opposite electrode 6 is obtained as asimulator. In FIG. 46, the electric potential in the window upperportion or lower portion is calculated when a white window has beendisplayed in the half tone of the relative transmission factor 50%.

It is desirable to correctly drive the liquid crystal to have thedriving electrode 5 between two opposite electrodes 6 so that thepotential distribution is symmetrical around the driving electrode 5. Itis found out from FIG. 46 that the potential distribution of an areanear the signal line 3 of the opening 50 is subjected to the influencesof the leakage of electric field caused between the signal line 3 andthe opposite electrode 6, thus resulting in asymmetric potentialdistribution. The electric field is caused along the surface of theglass substrate 1, thus causing a problem like crosstalk. For example,when a white window is displayed in such black displaying as shown inFIG. 47, there prises a problem on the display called “longitudinalcrosstalk” where the vertical luminance of the window portion changeswith respect to the other black displaying portion.

An example in a case of a normally black mode (wherein the displayingbecomes black with the voltage being not applied) will be described inFIG. 44. When such a window pattern in FIG. 47 is displayed, the samevoltage as that of the opposite electrode 6 is applied during theselecting period of the black displaying portion 111 upon the signalline 3 of the pixels of the window and its upper and lower portionsduring the picture face, and a voltage necessary to the white displaying113 is applied during the selecting period of the white displayingportion 111.

The voltage of a value where the absolute value of the electricpotential value between the electrodes has been averaged by hour isapplied upon the liquid crystal 11 effectively. Therefore, for example,when the black displaying and the white displaying are equal in theselecting period, the effective potential equal to the half tone display112 is applied upon these pixels between the signal line 3 and theopposite electrode 6. At this time, the liquid crystal on the slit 40between the signal line 3 and the opposite electrode 6 becomes atransmission mode by the electric field to horizontal to the glasssubstrate 1 to be caused between the signal line 3 and the oppositeelectrode 6. The electric field to be caused by the electrical potentialdifference between the signal line 3 and the opposite electrode 6 givesinfluences even upon the electric field between the driving electrode 5and the opposite electrode 6, so as to change the liquid crystal of theblack displaying portion into the transmission mode. As a result, thecrosstalk is caused.

In order to prevent such longitudinal crosstalk from being caused, theleaking light transmitting through the slit 40 between the signal line 3and the opposite electrode 6 is required to be shielded by the BM 12formed on the opposite substrate 30 and to prevent the electric field,caused between the signal line 3 and the opposite electrode 6, frombeing interfered with the electric field between the driving electrode 5and the opposite electrode 6 with the driving electrode 5 and theopposite electrode 6 spaced apart from the opposite electrode 6 of theside end portion on the side of the opening 50, and the signal line 3.When the driving electrode 5 and the opposite electrode 6 are separatedfrom the signal line 3 to make larger the width of the oppositeelectrode 6 adjacent to the signal line 3, and the aperture ratio of theopening 50, namely, a portion to be occupied by an area where the areaof the driving electrode 5 and the opposite electrode 6 and so on issubtracted from the area of the opening 50 with respect to the area ofthe opening 50 surrounded with broken lines in FIG. 4a, becomes smallerto make the picture quality worse. In order to develop the high picturequality liquid crystal displaying apparatus, it is necessary to shieledthe light, without reducing the aperture ratio, the electric field to becaused between the signal line 3 and the opposite electrode 6 adjacentto the signal line 3.

As clear from FIG. 43b, level of the surface of the passivation film 10′which is an upper layer film of the array substrate 20 is not flat(level difference), and the gap between the surface of the passivationfilm 10′ and the opposite substrate 30 is not flat. Thus, unevenluminance is likely to be caused, causing the picture quality worse. Thelevel difference provided makes not only the array substrate inferiordue to crack, but also disconnects the wiring on the array substrate dueto the level difference portion in the manufacturing operation with aproblem in improving the yield factor and reliability of the product.

Further, in accordance with the conventional IPS liquid crystaldisplaying apparatus, picture quality is deteriorated by light leakingtransmitted from the slit 40, the light being emitted by a back lightserving as a light sourse. In order to shield the leaked light, theblack matrix 12 is provided on the opposite substrate 30. However, whenthe TFT array substrate 20 is superposed with the opposite substrate 30,there might be generated error. Then, the black matrix 12 has beenformed in such a manner as to be somewhat larger with some margin forthe purpose of taking the error into consideration. However, therearises such a problem in which opening ratio is lowered when shiedingeffect is enhanced by making the black matrix 12 large.

The first object of the present invention is to solve the problemsmentioned above, and to provide an IPS liquid crystal displayingapparatus causing electric field parallel to a glass substrate, the IPSliquid crystal displaying apparatus capable of improving shieldingeffect against electric field leaking from the signal line, making theopening wide (that is, making opening ratio high) by lowering the lightshielding area. Further, the second object of the present invention isto provide a high quality IPS liquid crystal displaying apparatus inwhich cost for producing the apparatur is decreased by preventing thelines from disconnection thereby improving the yield factor.

SUMMARY OF THE INVENTION

The IPS liquid crystal displaying apparatus of the present inventioncomprises:

a TFT array substrate,

an opposite substrate opposed to the TFT array substrate and

liquid crystal interposed between the TFT array substrate and theopposite substrate,

wherein the TFT array substrate is composed of a glass substrate, a gateinsulating film formed on the glass substrate, a possivation film formedon the gate insulating film, a plurality of scanning lines fortransmitting a scanning signal, the plurality of scanning lines beingformed on the glass substrate, a plurality of signal lines fortransmitting an image signal, the plurality of signal lines being formedon the gate insulating film, a plurality of pixels arranged in grid likepattern by crossing the plurality of scanning lines with the pluralityof signal lines, a plurality of TFTs implementing switching operation ofthe image signal on the basis of the scanning signals, a plurality ofdriving electrodes connected with the TFT, a plurality of oppositeelectrodes arranged in such a manner that each of the plurality ofopposite electrodes is opposed to each of the driving electrodes, and aplurality of common lines for mutually connecting each of the oppositeelectrode of one of the plurality of pixels with the other one of theplurality of pixels,

wherein the TFT array substrate is formed on the passivation film, thepassivation film being different from a layer provided with the drivingelectrode and the opposite electrode.

The IPS liquid crystal displaying apparatus of the present invention isprovided with a driving electrode for driving the liquid crystal layerby causing the electric field parallel to the TFT array substrate face,the driving electrode being connected with the TFT, and an oppositeelectrode connected with a common line. At least the opposite electrodehas a TFT array substrate formed on the passivation film, different froma layer where the signal line is formed.

The IPS liquid crystal displaying apparatus of the present invention hasa TFT array substrate having an opposite electrode formed to cover oneportion of the signal line or all the portion of the signal line.

The IPS liquid crystal displaying apparatus of the present invention hasa TFT array substrate having an opposite electrode formed to cover oneportion of the scanning line or all the portion thereof, having at leastan opposite electrode in a layer different from the scanning line.

The IPS displaying apparatus of the present invention has a common lineand a scanning line on the same layer, and a signal line provided on thegate insulating film.

The IPS liquid crystal displaying apparatus of the present invention hasa TFT array substrate with the surface of the passivation film beingapproximately flat in shape.

The IPS liquid crystal displaying apparatus of the present invention hasa light shielding means formed to have the signal line and the oppositeelectrode superposed.

The IPS displaying apparatus of the present invention has a TFT arraysubstrate formed, to have for superposition in different layers, a TFTfor switching the picture image signal in accordance with the scanningsignal, a driving electrode for accumulating, while the switch of theTFT is off, the electric load stored when the switch of the TFT is on,and a storage capacitance increasing electrode for reinforcing thecapacitance of the driving electrode.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a sectional view showing the construction of one pixel of anIPS liquid crystal displaying apparatus of Embodiment 1 of the presentinvention;

FIG. 2 is a plain view showing the construction of one pixel of an IPSswitching type liquid crystal displaying apparatus of Embodiment 1 ofthe present invention;

FIGS. 3a and 3 b are a plain view and a sectional view showing theconstruction of one pixel of an IPS liquid crystal displaying apparatusof the embodiment 1 of the present invention;

FIGS. 4a, 4 b, 5 a, 5 b, 6 a, 6 b, 7 a, 7 b, 8 a and 8 b depict is aprocess flow of a TFT array substrate of an IPS liquid crystaldisplaying apparatus of Embodiment 1 of the present invention;

FIGS. 9a, 9 b, 10 a, 10 b, 11 a, 11 b, 12 a, 12 b, 13 a and 13 b depictis another process flow of a TFT array substrate of an IPS liquidcrystal displaying apparatus of Embodiment 1 of the present invention;

FIGS. 14a, 14 b, 15 a, 15 b, 16 a, 16 b, 17 a, 17 b, 18 a and 18 bdepict is a still another process flow of a TFT array substrate of anIPS liquid crystal displaying apparatus of Embodiment 1 of the presentinvention;

FIGS. 19a and 19 b are a plain view and a sectional view showing theconstruction of one pixel of an IPS liquid crystal displaying apparatusof Embodiment 2 of the present invention;

FIGS. 20a, 20 b, 21 a, 21 b, 22 a, 22 b, 23 a, 23 b, 24 a and 24 bdepict a process flow of a TFT array substrate of an IPS liquid crystaldisplaying apparatus of Embodiment 2 of the present invention;

FIGS. 25a and 25 b are a plain view and a sectional view showing theconstruction of one pixel of an IPS liquid crystal displaying apparatusof Embodiment 3 of the present invention;

FIGS. 26a, 26 b, 27 a, 27 b, 28 a, 28 b, 29 a, 29 b, 30 a and 30 bdepict a process flow of a TFT array substrate of an IPS liquid crystaldisplaying apparatus of Embodiment 3 of the present invention;

FIGS. 31a and 31 b are a plain view and a sectional view showing theconstruction of one pixel of an IPS liquid crystal displaying apparatusof Embodiment 4 of the present invention;

FIGS. 32a and 32 b are a plain view and a sectional view showing theconstruction of one pixel of an IPS liquid crystal displaying apparatusof Embodiment 5 of the present invention;

FIG. 33 is a view showing the potential distribution when the drivingelectrode and the opposite electrode are in a layer higher than theupper layer;

FIGS. 34a and 34 b are a plain view and a sectional view showing theconstruction of one pixel of an IPS liquid crystal displaying apparatusof Embodiment 6 of the present invention;

FIGS. 35a and 35 b are a plain view and a sectional view showing theconstruction of one pixel of an IPS liquid crystal displaying apparatusof Embodiment 7 of the present invention;

FIG. 36 is a sectional view showing the construction of one pixel of anIPS liquid crystal displaying apparatus of Embodiment 8 of the presentinvention;

FIGS. 37a, 37 b, 38 a, 38 b, 39 a, 39 b, 40 a, 40 b, 41 a, 41 b, 42 aand 42 b depict a process flow of a TFT array substrate of an IPS liquidcrystal displaying apparatus of Embodiment 9 of the present invention;

FIGS. 43a and 43 b are a plain view and a sectional view showing theconstruction of one pixel of the conventional IPS liquid crystaldisplaying apparatus;

FIG. 44 shows an equivalent circuit of one pixel of the conventional IPSliquid crystal displaying apparatus;

FIG. 45 is a block diagram showing the construction of the conventionalIPS liquid crystal displaying apparatus;

FIG. 46 is an explanatory view showing the electric potentialdistribution when the driving electrode and the opposite electrode arein a layer lower than the signal line; and

FIG. 47 an explanatory a view showing a crosstalk.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1

One embodiment of the present invention will be described in accordancewith drawings. The reference numerals in Embodiment 1 are the same asthose of the conventional reference numerals. FIG. 1 is a sectional viewshowing the construction of one pixel of the IPS type liquid crystaldisplaying apparatus in Embodiment 1 of the present invention. FIG. 2 isits plain view. FIG. 1 is a sectional view taken along a line of A—A inFIG. 2. Referring to the drawing, reference numeral 1 denotes a glasssubstrate, numeral 2 denotes a scanning line, numeral 3 denotes a signalline, numeral 4 denotes a TFT, numeral 5 denotes a driving electrode,numeral 6 denotes an opposite electrode, numeral 7 denotes an electrodefor forming the storage capacitance, numeral 8 denotes a common line,numeral 9 denotes a gate insulating film, numeral 10 denotes apassivation film, numeral 11 denotes a liquid crystal, numeral 12denotes a BM, numeral 14 denotes a contact hole, numeral 15 denotes asource electrode of the transistor, and numeral 16 denotes a drainelectrode of the transistor. Numeral 20 denotes an array substratecomprising a glass substrate 1, a signal line 3, a driving electrode 5,an opposite electrode 6. Numeral 30 denotes an opposite substratecerving as a displaying picture face arranged opposite to the arraysubstrate 20. Numeral 40 denotes a slit which is a gap between thesignal line 3 and the opposite electrode 6. Numeral 50 denotes anopening of a pixel. FIG. 3 depicts the construction of one pixel of theIPS type liquid crystal displaying apparatus when a channel passivationTFT 21 which is one type of a TFT 4 is provided as a TFT to be used inthe IPS type liquid crystal displaying apparatus shown in FIG. 2. FIG.3a is its plain view. FIG. 3b is a sectional view.

The construction of the pixel of the IPS type liquid crystal displayingapparatus will be described in accordance with FIG. 1 and FIG. 2.Referring to the drawings, numeral 1 denotes a glass substrate with ascanning line 2 being formed on the glass substrate 1. A gate insulatingfilm 9 is laminated to cover the scanning line 2 and a signal line 3 isprovided on the gate insulating film 9. A passivation film 10 islaminated on the signal line 3. A driving electrode 5 and an oppositeelectrode 6 are provided on the passivation film 10. The TFT arraysubstrate 20 is made as described above. A substrate 30 which isprovided to be opposed to the TFT array substrate 20 is an oppositesubstrate for grasping a liquid crystal 11 with respect to the TFT arraysubstrate 20. The IPS liquid crystal displaying apparatus of the presentinvention causes an electric field along the surface of the TFT arraysubstrate, and thereby to drive the liquid crystal 11 by controlling thedirection of the electric field.

FIG. 2 is a plain view of an IPS liquid crystal displaying apparatusshown in FIG. 1. Referring to FIG. 2, numeral 2 denotes a scanning lineand numeral 3 denotes a signal line. An area surrounded by the scanningline 2 and the signal line 3 becomes one pixel. Numeral 4 denotes a TFTprovided in the intersection point between the scanning line 2 and thesignal line 3. The gate electrode of three electrodes having the TFT 4is connected with the scanning line 2, and the source electrode 15 isconnected with the signal line 3. The drain electrode 16 of threeelectrodes having the TFT 4 is connected with the driving electrode 5 bya contact hole 14 in an upper layer through a passivation film 10 (notshown). An opposite electrode 6 which is provided opposite to be engagedwith the driving electrode 5 is connected with the common line 8 of thesame layer. The common line 8 not shown is connected with the oppositeelectrode 6 of the other adjacent pixel. The driving electrode 5, theopposite electrode 6, and the common line 8 are formed at the same timein a layer upper than the signal line 3.

Numeral 7 denotes storage capacitance for keeping the potential of thedriving electrode 5. The opposite electrode 6 and the drain electrode 16are laminated vertically. Numeral 40 denotes a slit between the signalline 3 and the opposite electrode 6. The BM 12 provided in the oppositesubstrate 30 shown in FIG. 1 shields the leakage light which transmitsthrough the slit 40 with the back light as a light source. Numeral 50denotes an opening. The larger the area of the opening becomes, thehigher picture quality the liquid display can obtain. As the IPS liquidcrystal displaying apparatus retains the electric charge stored in thedriving electrode 5 connected with the drain electrode 16 of the TFT 4and drives the liquid crystal 11 by causing the electric field along thesurface of the glass substrate 1, the opposite substrate 30 is ano-electrode substrate not provided with an electrode. One example ofthe process flow of the TFT array substrate for composing the pixel ofthe IPS liquid crystal displaying apparatus in Embodiment 1 will bedescribed.

FIGS. 4a, 4 b, 5 a, 5 b, 6 a, 6 b, 7 a, 7 b, 8 a and 8 b depict aprocess flow of a TFT array substrate. FIGS. 9a, 9 b, 10 a, 10 b, 11 a,11 b, 12 a, 12 b, 13 a and 13 b depict another process flow of a TFTarray substrate. FIGS. 14a, 14 b, 15 a, 15 b, 16 a, 16 b, 17 a, 17 b, 18a and 18 b depict still another process flow of a TFT array substrate.The left-hand side views of FIG. 4a through FIG. 18a show the TFT arraysubstrate and the right-hand side views thereof show the terminalportions for embodying the scanning line 2 into the scanning linedriving circuit. Referring to FIGS. 4a, 4 b, 5 a, 5 b, 6 a, 6 b, 7 a, 7b, 8 a and 8 b a step 1 (FIGS. 4a and 4 b) forms a scanning line 2, ofapproximately 50 nm through 800 nm in film thickness, under theconstruction of any one of Cr, Al, Mo, Ta, Cu, Al—Cu, Al—Si—Cu, Ti, W,or of their alloy, or transparent materials such as ITO (Indium TinOxide) or the like or the laminated thereof. The scanning line 2functions even as the gate electrode of the TFT 4. As an etching methodin forming the scanning line 2 may be used an etching method as thesection becomes rectangular although the taper etching which becomestrapezoidal in section is shown in FIGS. 4a, 4 b, 5 a, 5 b, 6 a, 6 b, 7a, 7 b, 8 a and 8 b.

In step 2 (FIGS. 5a and 5 b), a gate insulating film 9 is accumulated tocover the scanning line 2, amorphous silicon with impurities such asamorphous silicon, phosphorus and so on being doped in it iscontinuously accommodated, then amorphous silicon is patterned and theTFT 4 is formed with a channel etch type. A gate insulating film 9 isproper to have approximately 200 nm through 600 nm in thickness by usinga transparent insulating film such as silicon nitride, silicon oxide orthe like, film oxide of a gate electrode material (namely, a material ofthe scanning line 2) or their laminated films. Also, a micro crystalsilicon with impurities such as phosphorus or the like being doped in itcan be used as a material instead of amorphous silicon with impuritiessuch as phosphorus or the like being doped in it.

In step 3 (FIGS. 6a and 6 b) there is formed a signal line 3simultaneously with a source electrode 15 and a drain electrode 16 ofthe TFT 4. The signal line 3 functions as a source electrode 15. Thesignal line 3 is formed of any one of Cr, Al, Mo, Ta, Cu, Al—Cu,Al—Si—Cu, Ti, W or alloy mainly made of them, or alloy made chiefly ofthem, or a transparent material of such as ITO or the like or theirlaminated construction.

In step 4 (FIGS. 7a and 7 b) there is formed a passivation film 10 witha transparent insulating film of silicon nitride, silicon oxide and soon. In order to electrically connect the driving electrode 5 with thedrain electrode 16, the partial passivation film on the drain electrode16 of the TFT 4 is removed to form a contact hole 14. At this time, thegate insulating film 9 and the passivation film 10 are removed from theterminal portion of the scanning line 2 at the same time and thepassivation film 10 is removed from the terminal portion of the signalline 3 so that the external terminal, the scanning line 2 and the signalline 3 can be connected electrically.

In step 5 (FIGS. 8a and 8 b) there is formed the driving electrode 5 andthe opposite electrode 6, as an electrode for forming the electric fieldin a horizontal direction to the substrate face, with any one of Cr, Al,Mo, Ta, Cu, Al—Cu, Al—Si—Cu, Ti, W or alloy mainly composed of at leasttwo thereof, or a transparent material of such as ITO or the like ortheir laminated construction or their laminated construction includingthem. The driving electrode 5 is connected with the drain electrode 16through the contact hole 14. The opposite electrode 6 is connected withthe common line 8. The opposite electrodes 6 are superposed through thedrain electrode 16 and the passivation film 10 to form the storagecapacitance 7 for keeping the electric potential of the drivingelectrode. By the above five steps, the driving electrode 5 and theopposite electrode 6 are provided in the layer (namely, on the side ofthe opposite substrate 30) upper than the signal line 3. The TFT arraysubstrate 20 which can apply the horizontal electric field to thesubstrate face can be made by using a channel etch type TFT with fivephoto-lithography processes.

Although the terminal 22 is formed by using the metal of the same layeras that of the scanning line 2 in the process flow of the abovedescribed TFT array substrate, a terminal can be formed by using theITO. The ITO has only to be made of the same layer as that of thescanning line or the signal line 3. Although the signal wiring has beenstraightly etched, it is desirable to conduct a taper etching operation.When the signal line is formed on Cr under the Al laminatedconstruction, an over etching operation is conducted in Cr when the Crhas been patterned after the Al is patterned, the construction becomesprotective in construction, causing disconnection. In order to preventit, the etching of Al is conducted again after the patterning of the Cr.Retreat the Al from the Cr end face and the protecting construction canbe prevented. This etching of the Al can use the taper etching. Thismethod can be adapted when the signal line is formed under the laminatedconstruction of different metals of two types or more of any one of Cr,Al, Mo, Ta, Cu, Al—Cu, Al—Si—Cu, Ti, W or alloy mainly composed of atleast two thereof, or transparent materials such as ITO or theirlaminated construction.

In FIGS. 4a, 4 b, 5 a, 5 b, 6 a, 6 b, 7 a, 7 b, 8 a and 8 b the drivingelectrode 5 and the opposite electrode 6 can be formed on the same layerand the driving electrode 5 and the signal line 3 are formed at the sametime as shown in FIGS. 9a, 9 b, 10 a, 10 b, 11 a, 11 b, 12 a, 12 b, 13 aand 13 b. After forming the passivation film 10 by using the siliconnitride or the like, the opposite electrode 6 can be formed. In thiscase, the driving electrode 5 and the opposite electrode 6 are formed ina separate layer. A channel passivation film transistor 21 which is onetype of TFT 4 can be used, instead of a TFT used for the TFT arraysubstrate shown in FIGS. 4a, 4 b, 5 a, 5 b, 6 a, 6 b, 7 a, 7 b, 8 a and8 b. FIGS. 14a, 14 b, 15 a, 15 b, 16 a, 16 b, 17 a, 17 b, 18 a and 18 bare views showing a process flow of the TFT array substrate formed byusing a channel passivation film transistor 21.

The TFT array substrate shown in FIGS. 14a, 14 b, 15 a, 15 b, 16 a, 16b, 17 a, 17 b, 18 a and 18 b includes a pixel of the IPS liquid crystaldisplaying apparatus shown in FIG. 3, and is formed much more in branchlayer than the TFT array substrate shown in FIG. 5. This is due to thedifference of a producing step (FIGS. 15a and 15 b) of forming ascanning line 2, then the continuously depositing the gate insulatingfilm 9, the amorphous silicon, and the channel passivation film to coverthe scanning line 2, then forming the channel passivation film 21,ion-injecting the impurities such as P and so on into the amorphoussilicon with the channel passivation film 21 as a mask to form ann-layer, and forming the channel passivation film transistor.

In the characteristic construction of the TFT array substrate 20 of theIPS liquid crystal displaying apparatus of Embodiment 1, the drivingelectrode 5 and the opposite electrode 6 on the array substrate 20 arearranged on a layer (namely, on the side of the opposite substrate 30)upper than the signal line 3. This arrangement allows a step of formingthe contact hole 14 and removing the passivation film 10 from theterminal portion of the signal line 3, and a step of removing theinsulating film 9 and the passivation film 10 from the terminal portionof the scanning line 2 to carry out at one time. Thus, the number of themasks can be reduced by one and thereby the manufacturing cost can bereduced.

It has been found by forming the driving electrode 5 and the oppositeelectrode 6 on the layer of the side of the opposite substrate 30 withthe signal line 3 and the layer being made different that the influencesof the electric field caused by the electric potential differencebetween the opposite electrode 6, provided adjacently to the signal line3 on the end portion of the opening 50 shown in FIG. 2, and the signalline 3, as judged from the description to be mentioned later inEmbodiment 5. Thus, the opposite electrode of the side end portion ofthe opening 50 can be made closer to the signal line 3 and the area ofthe opening 50 can be made larger.

In FIG. 1, the driving electrode 5 and the opposite electrode 6 aredirectly in contact with the liquid crystal interposed between the TFTarray substrate 20 and the opposite substrate 30, so that the liquidcrystal can be efficiently driven, and the space between the drivingelectrode 5 and the opposite electrode 6 can be made wider. Thus, aneffect of improving the aperture ratio can be obtained.

Embodiment 2

FIGS. 19a and 19 b show the construction of the pixel electrode of theliquid crystal displaying apparatus of the embodiment 2 of the presentinvention. FIG. 19a is its plain view. FIG. 19b is a sectional viewtaken along a line of A—A of FIG. 19a. FIGS. 20a, 20 b, 21 a, 21 b, 22a, 22 b, 23 a, 23 b, 24 a and 24 b are views showing the process flow ofthe array substrate. Referring to the drawing, reference numeral 1denotes a glass substrate, numeral 2 denotes a scanning line, numeral 3denotes a signal line, numeral 4 denotes a thin film transistor (TFT),numeral 5 denotes a driving electrode, numeral 6 denotes an oppositeelectrode, numeral 7 denotes an electrode for forming the storagecapacitance, numeral 8 denotes common line, numeral 9 denotes a gateinsulating film, numeral 10 denotes a passivation film, numeral 11denotes a liquid crystal, numeral 12 denotes a BM, numeral 14 denotes acontact hole, numeral 15 denotes a source electrode of a transistor, andnumeral 16 denotes a drain electrode. Numeral 18 denotes a through-hole,numeral 20 denotes an array substrate comprising a glass substrate 1, asignal line 3, a driving electrode 5, an opposite electrode 6. Numeral30 denotes an opposite substrate serving as a display picture facearranged opposite to the array substrate 20. Numeral 40 denotes a slitwhich is a gap between the signal line 3 and the opposite electrode 6.Numeral 50 denotes an opening of the pixel.

In Embodiment 1, the common line 8 is formed on the same layer as thatof the opposite electrode 6. In the embodiment 2, the common line 8 isformed on the same layer as that of the scanning line 2, namely, on theglass substrate 1 as shown in FIGS. 20a, 20 b, 21 a, 21 b, 22 a, 22 b,23 a, 23 b, 24 a and 24 b. The source electrode 15 is connected with thesignal line 3, which is laminated on the scanning line 2 and the commonline 8 through the gate insulating film 9. Furthermore, the drivingelectrode 5 and the opposite electrode 6 are formed through thepassivation film 10. The driving electrode 5 is connected with the drainelectrode 16 through the contact hole 14. The opposite electrode 6 isconnected with the common line 8 through the through-hole 18. Thechannel passivation film TFT can be used as the TFT 4.

In the IPS liquid crystal displaying apparatus of Embodiment 2, as inEmbodiment 1, the driving electrode 5 and the opposite electrode 6 areformed in a layer close to the liquid crystal different from the signalline 3. As the liquid crystal can be driven more efficiently, the spacebetween the driving electrode 5 and the opposite electrode 6 can be madewider to improve the aperture ratio. Since the common line 8 and thescanning line 2 are formed in the same layer, the common line 8 can beformed on the flat glass substrate 1 together with the scanning line 2.Thus, a problem of disconnecting the common line 8 with a leveldifference portion is prevented from being caused, so as to improvetraction defective. Therefore, the reliability of the product isimproved. In Embodiment 1, the opposite electrode 6 cannot be madethinner in film due to resistivity of the common line 8, but inEmbodiment 2, the film of the opposite electrode 6 can be made thinner.The dispersion of the electrode space is made smaller due to the thinnerfilm of the opposite electrode 6, so as to realize a liquid crystaldisplaying apparatus which is less in uneven luminance across the wholepicture face.

Embodiment 3

FIGS. 25a and 25 b show the construction of one pixel of the liquidcrystal displaying apparatus of the embodiment 2 of the presentinvention. FIG. 25a is its plain view. FIG. 25b is a sectional viewtaken along a line of A—A of FIG. 25a. FIGS. 26a, 26 b, 27 a, 27 b, 28a, 28 b, 29 a, 29 b, 30 a and 30 b are views showing the process flow ofthe array substrate. Referring to the drawing, reference numeral 1denotes a glass substrate, numeral 2 denotes a scanning line, numeral 3denotes a signal line, numeral 4 denotes a TFT, numeral 5 denotes adriving electrode, numeral 6 denotes an opposite electrode, numeral 7denotes an electrode for forming the storage capacitance, numeral 8denotes common line, numeral 9 denotes a gate insulating film, numeral10 denotes a passivation film, numeral 11 denotes a liquid crystal,numeral 12 denotes a BM, numeral 14 denotes a contact hole, numeral 15denotes a source electrode of a transistor, and numeral 16 denotes adrain electrode. Numeral 20 denotes an array substrate comprising aglass substrate 1, a signal line 3, a driving electrode 5, an oppositeelectrode 6. Numeral 30 is an opposite substrate serving as a displayingpicture face arranged opposite to the array substrate 20. Numeral 40denotes a slit which is a gap between the signal line 3 and the oppositeelectrode 6. Numeral 50 denotes an opening of the pixel.

In forming the TFT array substrate 20, the passivation film 10 is formedof a transparent insulation film such as silicon nitride, silicon oxide.The surface of the passivation film 10 is not flat and has a leveldifference. In Embodiment 3, the passivation film 10 is made flat byremoving the level difference of the surface of the passivation film 10,as shown in FIG. 25b and FIGS. 26a, 26 b, 27 a, 27 b, 28 a, 28 b, 29 a,29 b, 30 a and 30 b, by forming with the use of a material such asacrylic melamine, acrylic epoxy or the like having a function offlattening the surface of the layer to be formed.

The IPS liquid crystal displaying apparatus of Embodiment 3 can equallyconstitute with precision the gap between the surface of the arraysubstrate across the whole displaying picture face and the oppositesubstrate 30 by flattening the surface of the passivation film 10. Aliquid crystal displaying apparatus which is less in uneven brillianceacross the whole picture face can be made. The fraction defective whichis caused due to cracks or the like in the level difference portion ofthe passivation film 10 can be made smaller to improve the yield. A highquality liquid crystal displaying apparatus can be realized which isapplied equally in rubbing treatment necessary to the orientation of theliquid crystal by the flattening operation and is less in orientationdisturbing.

As in Embodiment 1, the driving electrode 5 and the opposite electrode 6are provided closer to the liquid crystal than a formed layer of thesignal line 3, with an effect of improving the aperture ratio, becausethe liquid crystal can be driven efficiently, and the space between thedriving electrode 5 and the opposite electrode 6 can be widened.

Embodiment 4

FIGS. 31a and 31 b show the construction of one pixel electrode of theliquid crystal displaying apparatus of Embodiment 4 of the presentinvention. FIG. 31a is its plain view. FIG. 31b is a sectional viewtaken along a line of A—A of FIG. 31a. Referring to the drawing,reference numeral 1 denotes a glass substrate, numeral 2 denotes ascanning line, numeral 3 denotes a signal line, numeral 4 denotes a TFT,numeral 5 denotes a driving electrode, numeral 6 denotes an oppositeelectrode, numeral 7 denotes an electrode for forming the storagecapacitance, numeral 8 denotes common line, numeral 9 denotes a gateinsulating film, numeral 10 denotes a passivation film, numeral 11denotes a liquid crystal, numeral 14 denotes a contact hole, numeral 15denotes a source electrode of, a TFT 4, and numeral 16 denotes a drainelectrode of the TFT. Numeral 20 denotes an array substrate composing aglass substrate 1, a signal line 3, a driving electrode 5, an oppositeelectrode 6. Numeral 30 denotes an opposite substrate serving as adisplaying picture face arranged opposite to the array substrate 20.Numeral 60 denotes a light shielding film provided on the glasssubstrate 1.

Embodiment 4 is characterized by formation of a light shielding film 60on a glass substrate 1, which shields the leakage light from a slit 40(see FIG. 43a) between the signal line 3 and the opposite electrode 6 inthe pixel structure of the liquid crystal displaying apparatus ofEmbodiment 1 through Embodiment 3. The structure of the liquid crystaldisplaying apparatus of Embodiment 4 will be described in accordancewith FIG. 31a and FIG. 31b.

A light shielding film 60 is formed on the glass substrate 1 in FIG.31b. Although not shown in FIG. 31b, the scanning line 2 is also formedon the same layer as that of the light shielding film 60. The scanningline 2 functions as a gate electrode of the TFT 4. A gate insulatingfilm 9 is laminated on the scanning line 2 and the light shielding film60. A signal line 3, in a position superposed on the light shieldingfilm 60, on the gate insulating film 9. The TFT 4 is also formed on thegate insulating film 9. The TFT 4 can use either of the channel etch TFTand the channel passivation film TFT. The source electrode 15 of the TFT4 and the drain electrode 16 are also formed in the same layer as thatof the signal line 3, so as to laminate the passivation film 10.Continuously a contact hole 14 is formed in the passivation film 10. Thedriving electrode 5 provided on the passivation film 10 and the drainelectrode of the TFT 4 provided on the gate insulating film 9 areconnected with each other through the contact hole 14.

The opposite electrode 6 is formed on the passivation film 10 as in thedriving electrode 5. In a position where the opposite electrode 6 issuperposed on the light shielding film 60, it is superposed through thedrain electrode 16 and the passivation film 10 to form the storagecapacitance 7 for keeping the electric potential of the drivingelectrode 5. The opposite electrode 6 is connected with the common line8 provided on the same layer. Broken lines are shown on both the endportions of the pixel of FIG. 31a. The broken lines show a position inFIG. 31a of the light shielding film 60 provided on the glass substrate1 shown in FIG. 31b. As shown by the broken lines, it is found out thata slit 40 (see FIG. 43a) is covered between the signal line 3 and theopposite electrode 6 by formation of the opposite electrodes 6 at boththe ends to be superposed on the light shielding film 60.

In Embodiment 4, the driving electrode 5 and the opposite electrode 6are formed on the passivation film 10. The driving electrode 5 and thesignal line 3 are formed simultaneously on the gate insulating film 9and the opposite electrode 6 can be formed after the passivation filmhas been formed by using silicon nitride or the like. In this case, thedriving electrode 5 and the opposite electrode 6 are formed in adifferent layer. In Embodiment 4, the light leaking from the slit 40(not shown) between the signal line 3 and the opposite electrode 6 isnot caused by formation of the light shielding film 60 on the glasssubstrate 1. Thus, the width of the BM 12 of the opposite substrate 30can be made narrower and the light shielding in the direction of thesignal line 3 do not have to be conducted by the BM 12. Therefore, theBM 12 can be omitted so that the opening portion can be provided larger.

The liquid crystal displaying apparatus is manufactured by superposedcombination between the TFT array substrate and the opposite substratewith a color filter attached to it, including the liquid crystal 11 intobetween these substrates, and connecting the driving circuit. Superposederrors are sometimes caused by a step of superposing the TFT arraysubstrate and the opposed substrate. Thus, in the BM, the lightshielding area has to be provided larger (see FIG. 43a), considering thesuperposed errors, so as to positively shield the leakage light from theslit 40 of the TFT array substrate 20. The transmission portion of theslit leakage light can be shielded in light positively by provision ofthe light shielding film 60 on the TFT array substrate 20. Thesuperposed error between the TFT array substrate and the oppositesubstrate is not necessary to be considered. Thus, the BM 12 can beprovided into the size of a necessary minimum, and thereby the openingportion can be made larger.

In the IPS liquid crystal displaying apparatus of Embodiment 4, thedriving electrode 5 and the opposite electrode 6 are provided in a layerclose to the liquid crystal as in the IPS liquid crystal displayingapparatus of Embodiment 1. The liquid crystal can be driven effectivelyand the space between the electrodes can be widened, with an effect ofimproving the aperture ratio.

Embodiment 5

A construction of one pixel of the IPS liquid crystal displayingapparatus of Embodiment 5 is depicted in FIGS. 32a and 32 b. The plainview thereof is depicted in FIG. 32a. FIG. 32b is a sectional view takenalong a line A—A of FIG. 32a. Referring to the drawing, referencenumeral 1 denotes a glass substrate, numeral 2 denotes a scanning line,numeral 3 denotes a signal line, numeral 4 denotes a thin filmtransistor (TFT), numeral 5 denotes a driving electrode, numeral 6denotes an opposite electrode, numeral 7 denotes an electrode forforming the storage capacitance, numeral 8 denotes common line, numeral9 denotes a gate insulating film, numeral 10 denotes a passivation film,numeral 11 denotes a liquid crystal, numeral 12 denotes a BM, numeral 14denotes a contact hole, numeral 15 denotes a source electrode of atransistor, and numeral 16 denotes a drain electrode of a transistor.Numeral 20 denotes an array substrate comprising glass substrate 1, asignal line 3, a driving electrode 5, an opposite electrode 6. Numeral30 denotes an opposite substrate serving as a displaying picture facearranged opposite to the array substrate 20.

Embodiment 5 is characterized by formation of the driving electrode 5and the opposite electrode 6, as in Embodiment 1, in a layer upper thanthe signal line 3, and furthermore, the formation of the oppositeelectrode 6 to cover the signal line 3, so as to make it hard to receivethe influences of the leakage electric field from the signal line 3 butfurther, not to cause the leakage light from the slit 40 (see FIG. 43a)between the signal line 3 and the opposite electrode 6. FIG. 33 depictsthe simulated results of changes in electric potential caused betweenthe driving electrode 5 formed to cover the signal line 3 and theopposite electrode 6 formed in the same layer as that of the drivingelectrode 5. FIG. 33 is the calculated electric potential in the windowupper portion or lower portion when a white window has been displayed onthe half tone of 50% in relative transmission factor.

Between FIG. 46 and FIG. 33 there is shown the electric potentialdistribution in the TFT array substrate of the conventional IPS liquidcrystal displaying apparatus having the driving electrode 5 and theopposite electrode 6 in the layer lower than the signal line 3. In FIG.33, the electric field to be caused by the electric potential differencebetween the signal line 3 and the opposite electrode 6 is shielded bythe opposite electrode 6 arranged on the upper portion to cover thesignal line 3. Thus, the electric potential distribution isapproximately symmetrical in the area close to the signal line 3 of theopening 50 and the area separated from the signal line 3.

In this manner, the TFT array substrate 20 of the IPS liquid crystaldisplaying apparatus of Embodiment 5 can reduce remarkably theinfluences, of the electric field to be caused between the signal line 3and the opposite electrode 6, with respect to the electric field to becaused between the driving electrode 5 and the opposite electrode 6 byformation of the driving electrode 5 and the opposite electrode 6 in alayer upper than the signal line 3, and formation of the oppositeelectrode 6 to cover the signal line 3. The opposite electrode 6 of theend of the opening 50 can be made much closer to the signal line 3, thusmaking it possible to widen the total area of the opening 50 wider.

As the opposite electrode 6 is formed to cover the signal line 3, theleakage light can be shield, thus making it possible to remove the BM12. As the area of the opening portion 50 can be widened, a liquidcrystal displaying apparatus higher in brilliance can be provided. As astep of providing the BM 12 can be reduced, the productivity can beimproved, and a liquid crystal displaying apparatus can be produced withlower cost. As in Embodiment 1, the driving electrode 5 and the oppositeelectrode 6 can be formed in a layer close to the liquid crystal. Theliquid crystal can be driven efficiently and the space between theelectrodes can be widened, thus improving the aperture ratio.

Embodiment 6

FIGS. 34a and 34 b show the construction of one pixel of the IPS liquidcrystal displaying apparatus of Embodiment 6. FIG. 34a is its plainview. FIG. 34b is a sectional view taken along a line of A—A of FIG.34a. The construction of the pixel of the IPS liquid crystal displayingapparatus of Embodiment 6 shown in FIGS. 34a and 34 b are fundamentallysimilar to that of the pixel of the IPS displaying apparatus ofEmbodiment 5 shown in FIG. 12, the description thereof is omitted.Although the opposite electrode 6 of the construction for completelycovering the signal line 3 is provided in Embodiment 5, the oppositeelectrode 6 of the construction for covering one portion of the signalline 3 can be used as in the opposite electrode 6 of the pixel of theIPS liquid crystal displaying apparatus of Embodiment 6 shown in FIGS.34a and 34 b.

According to Embodiment 6, the opposite electrode 6 is adapted to formone portion of the signal line 3. Thus, the electric field forgenerating the electric potential difference between the signal line 3and the opposite electrode 6 can reduce the influences for influencingthe electric field between the driving electrode 5 and the oppositeelectrode 6, and the leakage light passing through the slit 40 betweenthe signal line 3 and the opposite electrode 6 can be shielded. It ispossible to make the width of the BM 12 narrower or remove the BM 12. Aliquid crystal displaying apparatus which is wider in an opening andhigher in luminance can be realized. Also, a process of providing the BM12 can be reduced by removing the BM 12, so as to improve theproductivity. As a superposed area of the signal line 3 and the oppositeelectrode 6 becomes smaller, the short-circuit defect between the signalline 3 and the opposite electrode 6 can be reduced. As the superposedarea of the signal line 3 and the opposite electrode 6 becomes smaller,the capacitance between the signal line 3 and the opposite electrode 6can be made smaller, so that the load of the wiring can be reduced,making it easier to do a driving operation.

Embodiment 7

FIGS. 35a and 35 b show the construction of one pixel of the IPS liquidcrystal displaying apparatus of Embodiment 7. FIG. 35a is its plainview. FIG. 35b is a sectional view taken along a line of A—A of FIG.35a. As the construction of the pixel of the IPS liquid crystaldisplaying apparatus of Embodiment 7 shown in FIGS. 35a and 35 b arefundamentally similar to that of the pixel of the IPS type displayingapparatus of the embodiment 5 shown in FIGS. 34a and 34 b, thedescription thereof is omitted. Embodiment 7 is characterized byenlarging the opposite electrode 6 up to above the scanning line 2, andconnecting the opposite electrode 6 of the other pixel adjacent to thepixel by using the opposite electrode 6, in the pixel construction ofthe liquid crystal displaying apparatus in, for example, Embodiment 6 asshown in FIGS. 34a and 34 b.

By using such a construction, the width of the opposite electrode 6becomes thicker so that the resistivity of the opposite electrode 6 islowered and the load is reduced, making it easier to conduct a drivingoperation. As the electric potential is supplied from the oppositeelectrode 6 on the scanning line 2 even when the common line 8 isdisconnected, it does not become defective on display. The reliabilityof the product is improved. The construction of the opposite electrode 6in Embodiment 7 can be adapted to not only to Embodiment 7, but also theother embodiments.

Embodiment 8

FIG. 36 shows the sectional construction of the storage capacitanceportion of one pixel of the liquid crystal displaying apparatus ofEmbodiment 8 of the present invention. Referring to the drawing,reference numeral 17 denotes an electrode for increasing the storagecapacitance formed on the glass substrate 1. Numeral 16 denotes a drainelectrode of the TFT. The storage capacitance portion of the liquidcrystal liquid displaying apparatus of Embodiment 8 as shown in thedrawing is superposed and laminated on a layer (for example, the layerof the scanning line 2) separate from the drain electrode 16 of the TFTthrough the gate insulating film 9. It can make the area of theelectrode for forming the storage capacitance smaller by the laminatingconstruction of the electrode of the storage capacitance portion. As aresult, the opening 50 (not shown) of the pixel can be made wider.

Embodiment 9

FIGS. 37a, 37 b, 38 a, 38 b, 39 a, 39 b, 40 a, 40 b, 41 a, 41 b, 42 aand 42 b are views showing the process flow of the TFT array substrateof the Embodiment 9. Referring to FIGS. 37a, 37 b, 38 a, 38 b, 39 a, 39b, 40 a, 40 b, 41 a, 41 b, 42 a and 42 b, reference numeral 1 denotes aglass substrate, numeral 2 denotes a scanning line, numeral 3 is asignal line, numeral 4 denotes a TFT, numeral 5 denotes a drivingelectrode, numeral 6 denotes an opposite electrode, numeral 8 denotescommon line, numeral 9 denotes a gate insulating film, numeral 10denotes a passivation film, numeral 14 denotes a contact hole, numeral15 denotes a source electrode of a transistor, and numeral 16 denotes adrain electrode of a transistor. Numeral 19 denotes a second passivationfilm. Numeral 20 denotes an array substrate comprising a glass substrate1, a signal line 3, a driving electrode 5, an opposite electrode 6.

In Embodiment 9, a second passivation film 19 is formed on the TFT arraysubstrate shown in FIGS. 4a through 18 a and FIGS. 4b through 18 b. Theconstruction of one pixel of the liquid crystal displaying apparatus ofEmbodiment 9 is similar to Embodiment 1. A method of manufacturing theliquid crystal displaying apparatus of the embodiment will be describedhereinafter. The process flow of the TFT array substrate in Embodiment 9is similar to Embodiment 1 up to a step for forming the oppositeelectrode 6. In Embodiment 9, a second passivation film 19 is formed onthe top layer of the opposite electrode 6.

By forming the second passivation film 19 between the driving electrode5 and the opposite electrode 6, the short circuit, between the drivingelectrode 5 and the opposite electrode 6, due to foreign materials canbe prevented to improve the yield. As the level difference between thedriving electrode 5 and the opposite electrode 6 can be made flat, ahigh quality of liquid crystal displaying apparatus can be realizedwhere the rubbing treatment necessary for the liquid crystal orientationis equally applied and is less in orientation disturbing.

According to the IPS liquid crystal displaying apparatus of the presentinvention, the driving electrode and the opposite electrode are formedin a layer close to the liquid crystal different to the signal line. Thedriving electrode and the opposite electrode are formed in a layer closeto the liquid crystal so that the liquid crystal can be driven moreefficiently. Thus, the space between the driving electrode and theopposite electrode can be widened, so as to improve the aperture ratio.

According to the IPS liquid crystal displaying apparatus of the presentinvention, at least the opposite electrode of the driving electrode andthe opposite electrode is formed in a layer close to the liquid crystaldifferent from a layer where the signal line is formed, so thatinfluences given by the electric field to be caused by the electricpotential difference between the signal line and the opposite electrode.

According to the IPS liquid crystal displaying apparatus of the presentinvention, the opposite electrode is formed to cover one portion or allthe portion of the signal line. The electric field to be caused by theelectric potential difference between the signal line and the oppositeelectrode influences the electric field to be caused between the drivingelectrode of the opening and the opposite electrode, thereby restraininga problem of deteriorating the picture quality on the displaying frombeing caused. Thus, the liquid crystal display of high picture qualitycan be made and the leakage light from between the signal line formaking the black light a light source, and the opposite electrode can beshielded accurately. The BM can be removed, so as to improve theaperture ratio.

According to the IPS liquid crystal displaying apparatus of the presentinvention, at least the opposite electrode is provided in a layerdifferent from the scanning line so as to cover one portion or all theportion of the scanning line. The opposite electrode of the other pixelcan be connected by the opposite electrode, so that the width of theopposite electrode can be made thicker without reduction in the area ofthe opening. Accordingly, the resistivity of the opposite electrode canbe lowered to reduce the load of the wiring. As the electric potentialcan be fed from the opposite electrode on the scanning line when thecommon line is disconnected, the reliability can be increased byrestraining the defects on the displaying from being caused.

According to the IPS liquid crystal displaying apparatus of the presentinvention, the common line and the scanning line are provided on thesame layer and the single line is provided on a layer closer to theopposite substrate than to the common lineand the scanning line. Thedefect to be caused in the stage difference portion can be restrained.

According to the IPS liquid crystal apparatus of the present invention,a passivation film whih formed approximately flat in surface where theTFT array substrate comes into contact with the liquid crystal. Thus,the gap between the array substrate surface and the opposite substrateacross all the display picture surface is equally constructed withprecision. The rubbing treatment necessary for the liquid crystalorientation is equally applied and the orientation disturbing can bereduced. The liquid crystal displaying apparatus which is less in unevenluminance across the whole picture face can be realized. The fractiondefective which is caused by cracks in the stage difference portion ofthe passivation film becomes smaller, so as to improve the yield.

In the IPS liquid crystal displaying apparatus of the present invention,a TFT array substrate is provided having a light shielding means formedto have the signal line and the opposite electrode superposed. Theleakage light for transmitting through the slit can be shielded, andthus the BM provided on the opposite substrate becomes unnecessary. Thesuperposed errors are not necessary to be considered in thesuperposition between the TFT array substrate and the opposite substratein determining the size of the light shielding means. Thus, the size ofthe light shielding means can be made that of a necessary minimum, so asto improve the aperture ratio.

According to the in plain switching type liquid crystal displayingapparatus of the present invention, a TFT array substrate formed to besuperposed with a TFT, a driving electrode, and a storage capacitanceincreasing electrode being different in layer. The area of the electrodefor forming the storage capacitance can be made smaller and the openingportion of the pixel can be made wider correspondingly, and the liquidcrystal displaying apparatus higher in luminance can be realized.

Though several embodiments of the present invention are described above,it is to be understood that the present invention is not limited only tothe above-mentioned, various changes and modifications may be made inthe invention without departing from the spirit and scope thereof.

What we claim is:
 1. An IPS liquid crystal displaying apparatus,comprising: a TFT array substrate; an opposite substrate opposed to saidTFT array substrate; a liquid crystal interposed between said TFT arraysubstrate and said opposite substrate, said TFT array substratecomprising: a glass substrate, a gate insulating film formed on saidglass substrate, and a passivation film formed on said gate insulatingfilm; a plurality of scanning lines configured to transmit a pluralityof scanning signals and formed on said glass substrate; a plurality ofsignal lines configured to transmit a plurality of image signals andformed on said gate insulating film; a plurality of common linesconfigured to transmit a plurality of common signals; a plurality ofpixels arranged in a grid like pattern by crossing said plurality ofscanning lines with said plurality of signal lines; a plurality of TFTsimplementing a switching operation of said plurality of image signalsbased on said plurality of image signals and said plurality of scanningsignals; a plurality of driving electrodes formed on said passivationfilm and connected with said plurality of TFTs; a plurality of oppositeelectrodes formed on said passivation film, each of said plurality ofopposite electrodes opposing each of said plurality of drivingelectrodes; and a plurality of common lines configured to connect eachof said plurality of opposite electrodes in each of said plurality ofpixels, wherein each of said plurality of driving electrodes isconfigured to drive said liquid crystal by generating an electric fieldwhich is parallel to a face of said TFT array substrate, between saidplurality of driving electrodes and said plurality of oppositeelectrodes, wherein each of said plurality of opposite electrodes isconfigured to be connected with each of said plurality of said commonlines, and wherein one of said plurality of opposite electrodes coversat least a portion of said plurality of signal lines, which is parallelto a respective one of said opposite electrodes.